Surgery remains the standard treatment for stage I-IIIA non-small cell lung care (NSCLC) and is the only modality associated with a meaningful long-term survival. Despite its central role, compared to chemotherapy and radiation, there are very few randomized controlled trials (RCTs) evaluating the surgical management of lung cancer, particularly in the elderly. Consequently, there are several areas of uncertainty regarding the surgical management of these patients. The goal of this application is to use national, population-based data to compare the effectiveness of several key surgical therapies for elderly patients with resectable NSCLC. The specific aims of the study are to: 1) compare the perioperative outcomes (perioperative mortality, post operative complications, length of stay, and costs) of NSCLC patients treated with video assisted thoracoscopy (VATS) vs. conventional (open) resection; 2) assess the long-term effectiveness (overall and lung cancer- specific survival) of VATS compared to open resection for the treatment of patients with resectable NSCLC; 3) determine whether survival after limited resection is equivalent to that after lobectomy in patients with stage IA bronchioloalveolar cell carcinoma; 4) evaluate the effectiveness of radiation therapy following limited resection of patients with stage I-II NSCLC. To address these aims, we will use data from the Surveillance, Epidemiology, and End Results (SEER) registry linked to Medicare claims. The study cohort will be comprised of all patients >65 years with histologically confirmed stage I-IIIA NSCLC diagnosed between 1992 and 2005. In each Specific Aim, we will apply strict inclusion and exclusion criteria, perform subgroup and stratified analyses, and use several statistical methods (propensity scores, instrumental variable, and sensitivity analyses) to control for selection bias. This study will fill an important gap in knowledge regarding the effectiveness of several surgical treatments that have been broadly adopted into clinical practice yet there is little data about their efficacy. Thus, the findings from this project will provide information that can directly impact the care of a large number of elderly patients with lung cancer and inform the design of future trials of treatment strategies.